A vacuum blood collection tube is widely used in biochemical tests, blood sugar measurement, erythrocyte sedimentation rate tests, blood coagulation measurement, serological tests, and hematological tests because of its easy operation for blood collection. Conventionally, as the vacuum blood collection tube, one in which a rubber stopper that can be pierced with a blood collection needle is attached to a bottomed tube having an opening has been known. For example, such a vacuum blood collection tube is disclosed in Japanese Patent Laid-Open No. 2005-253538 (pages 6 to 10, FIG. 1) and Japanese Patent Laid-Open No. 2005-261965 (pages 6 to 8, FIG. 1). In a conventional vacuum blood collection tube, before blood collection, the stopper is attached to the opening of the bottomed tube, and the stopper is in close contact with the opening of the bottomed tube, so that the reduced pressure state inside the bottomed tube is maintained. During blood collection, one end of a blood collection needle is inserted into a blood vessel of a subject, and then, the other end of the blood collection needle is pierced into the needle-piercing portion of the stopper. Then, due to the pressure difference between the pressure inside the blood vessel and the pressure inside the bottomed tube, the collection of blood from the subject is performed. Thus, in the conventional vacuum blood collection tube, blood collection can be performed by a vacuum blood collection method. Even after the blood collection needle is pulled out, the rubber stopper is elastically deformed to close the needle hole, so that liquid tightness is kept. Therefore, the collected blood sample (also referred to as a specimen) is prevented from leaking from the needle hole during blood collection.
Generally, in each of the above-described tests using the vacuum blood collection tube, a blood test should be performed as soon as possible after blood collection. In a blood sample collected in the vacuum blood collection tube, the cold activation of complement occurs, so that the blood specimen is quickly subjected to each test rather than being held at low temperature. Therefore, so far, the blood sample collected in the vacuum blood collection tube has not been preserved as whole blood for a long period of several days or more. In other words, so far, the purpose of development has not been to store blood after blood collection, in the vacuum blood collection tube, for a long period.
On the other hand, in recent years, a test for examining the relationship between the genes of a patient and the effect and side effect of various medicines to provide medication and a treatment method suitable for the individual patient (PGx test) has been performed in parallel with clinical research and a clinical trial. In the PGx test, whole blood is generally used for the analysis of DNA diversity, RNA expression, and the like.
In the PGx test, blood cell components themselves of blood are not the objects to be tested, and DNA present in the nucleus of a nucleated cell, such as a white blood cell and a lymphocyte, or RNA (mRNA) made using DNA as a template, and protein biosynthesized based on the RNA information are objects to be tested. Therefore, in the PGx test, unlike the above-described biochemical test, it is required that whole blood is frozen and stored at ultra-low temperature to prevent the decomposition of DNA, RNA, and protein. Also, when a blood sample once frozen is thawed again, DNA damage occurs, and DNA extraction efficiency decreases. Therefore, it is required that after a blood sample is frozen in a blood collection facility, the blood sample is stored at ultra-low temperature for a long period so as not to thaw again.
However, in the conventional vacuum blood collection tube, a plastic material, such as PET, is often used, as the material of the vacuum blood collection tube, and a material that can endure storage at ultra-low temperature is not used. Therefore, when it is attempted to cryopreserve the conventional vacuum blood collection tube as it is, low temperature fracture may occur when the conventional vacuum blood collection tube is immersed in liquid nitrogen. Also, in the conventional vacuum blood collection tube, a metal lid or a plastic lid is used to bring the stopper into close contact with the bottomed tube. But, different materials are often used for the bottomed tube, the stopper, and the lid, and when these are held at ultra-low temperature, a clearance may be produced between the stopper or the lid and the bottomed tube due to difference in the degree of thermal shrinkage. In such a case, from the clearance, external liquid nitrogen and the like may enter the vacuum blood collection tube, and the sample inside the vacuum blood collection tube may leak to the outside.
Therefore, when a whole blood specimen is stored, it is necessary to separately prepare a blood storage container for cryopreservation that can endure preservation at ultra-low temperature, and, after collecting blood in the vacuum blood collection tube, transfer the blood sample to the blood storage container. In this blood storage container, no clearance is produced even at ultra-low temperature, so that liquid tightness is kept. In other words, there is no possibility that from the clearance, external liquid nitrogen and the like enter the vacuum blood collection tube, and the sample inside the vacuum blood collection tube leaks to the outside. However, the operation of transferring the blood sample from the vacuum blood collection tube to the blood storage container not only requires labor for the operation itself, but also may cause the blood spilled or scattered during the operation. Therefore, effort and burden on the operator of the transferring operation are very large.